The present disclosure is directed generally to necking die carriers for manufacture of metal containers, such as aluminum cans and bottles, and methods of manufacture thereof. Metal containers are typically made by either an impact-extrusion process or by a cupper/bodymaker process. In the impact-extrusion process, a metal slug placed in a die is impacted by a high-speed cylindrical punch causing the metal to flow backwards along the punch creating the extruded cylindrical container. The cylinder is placed over an ironing punch and the walls are narrowed while lengthening occurs. In the cupper/bodymaker process, a blank made from sheet metal is pressed into a die to form a cup-shaped cylindrical container that is wider and shorter than the finished can. The container is then transferred to a bodymaker which performs a sequential series of wall-ironing operations to narrow the cup while lengthening and thinning the walls of the cylinder.
The diameter of the cylinder opening is often reduced to provide structural integrity, to form a neck, or to provide an attachment surface for a lid or cap. The diameter of the open cylinder is reduced in a process termed “die necking” in which the diameter at the open end is gradually decreased by pushing the cylinder longitudinally into successively narrower dies. A cylindrical necking die is reciprocated axially engaging the exterior of the container while a coaxial die pilot simultaneously is moved axially in a mating manner on the interior of open end of the container. In a similar process, dies of fixed diameter, but increasing distant tapering are used to place the neck further down the length of the container, in a process termed “deep necking”.
Because the necked diameter or distance of the taper of an aluminum cylinder can only be reduced in small increments due to wrinkling and tearing, the industry relies on large, high throughput machines to perform the die-necking process. Each container necking operation is performed in a necking module consisting of a rotatable turret with a plurality of identical exposed necking substations on the periphery thereof with each necking substation having a stationary necking die. For example, a conventional soda can has a diameter of 2 11/16 inches (a 211 container), while the neck has a diameter of 2 6/16 inches (a 216 neck) requiring the necking process be repeated numerous times with sequentially narrower dies. Different can fillers use cans of various sizes and lengths requiring the manufacturer to quickly adapt its necking machines and operations from one neck size to another. Any change in specification to the cylinder neck requires individually removing and replacing the dies. Thus, it would be desirable to have a necking device that is rapidly reconfigurable and more compact.